Break away door, trip unit and circuit breaker assembly including same

ABSTRACT

A hinge assembly includes a first portion having first and second receptacles and a second portion having first and second cylindrical members extending in opposite directions along a hinge axis and a thickened portion having a contoured outer surface disposed adjacent the cylindrical members. The second portion is moveable from: a first state wherein the first and second cylindrical members are disposed in the first and second receptacles such that the second portion is coupled to the first portion and generally free to rotate about the hinge axis through at least a predetermined degree range, and a second state in which the second portion is decoupled from the first portion responsive to the second portion being rotated beyond the predetermined degree range and the contoured outer surface interacting with a portion of the first portion.

BACKGROUND

1. Field

The disclosed concept relates generally to circuit breakers, and inparticular, to trip units for use in circuit breakers. The inventionfurther relates to access doors for use in trip units.

2. Background Information

Circuit interrupters, such as for example and without limitation,circuit breakers, are typically used to protect electrical circuitryfrom damage due to an overcurrent condition, such as an overloadcondition, a short circuit, or another fault condition, such as an arcfault or a ground fault. Circuit breakers typically include separablecontacts. The separable contacts may be operated either manually by wayof an operator handle or automatically in response to a detected faultcondition. Typically, such circuit breakers include an operatingmechanism, which is designed to rapidly open the separable contacts, anda trip mechanism, such as a trip unit, which senses a number of faultconditions to trip the breaker automatically. Upon sensing a faultcondition, the trip unit trips the operating mechanism to a trip state,which moves the separable contacts to their open position.

Some trip units include an access door which allows for easy access toswitches which control trip unit settings without requiring removal ofone or more covers which are typically secured to a housing of thecircuit breaker via screws or other suitable fasteners. Such accessdoors are typically formed from a clear plastic material. Suchconstruction provides a number of benefits. One of such benefits ofutilizing such a clear material is that the switches covered by suchaccess doors and thus the settings thereof may be readily viewed withoutrequiring the access door to be opened. Another benefit of using suchmaterial is the generally low cost of the material and forming thereof.

While there are a number of benefits of such present designs, there isstill room for improvement as access doors tend to be less than durableand may be rather easily broken if care is not taken. Typically, suchbreakage occurs when a technician is installing and/or servicing acircuit breaker and thus has the front cover removed. During such time,it is common to have the access door of the trip unit open for makingadjustments to the unit. Being formed from clear material, the accessdoor tends to not stand out and can be easily left in an open position.When disposed in the open position, the access door is generally fragileand can be rather easily broken, typically at the hinged portionthereof, if opened beyond its intended range. Such over-opening mayreadily occur if the access door is contacted while disposed in an openposition such as by a technician moving in the vicinity of the accessdoor or by attempting to install the front cover without having firstclosed the access door.

There is thus room for improvement in access doors for trip units.

There is also room for improvement in trip units employing access doors,and circuit breakers employing such trip units.

SUMMARY

These needs and others are met by embodiments of the disclosed conceptin which are directed to a hinge assembly. The hinge assembly comprisesa first portion and a second portion. The first portion includes a firstreceptacle and a second receptacle. The second portion includes a firstcylindrical member extending along a hinge axis in a first direction, asecond cylindrical member extending along the hinge axis in a seconddirection opposite the first direction, and a thickened portion having acontoured outer surface disposed adjacent the first cylindrical memberand the second cylindrical member. The second portion is moveable from:(i) a first state wherein the first cylindrical member is disposed inthe first receptacle and the second cylindrical member is disposed inthe second receptacle such that the second portion is coupled to thefirst portion and generally free to rotate about the hinge axis throughat least a predetermined degree range, and (ii) a second state in whichthe second portion is decoupled from the first portion responsive to thesecond portion being rotated beyond the predetermined degree range andthe contoured outer surface interacting with a portion of the firstportion.

Each of the first receptacle and the second receptacle may comprise amain portion defined at least in-part by a curved surface disposedgenerally a radial distance about the hinge axis, and when disposed inthe first state, the first cylindrical member is disposed in the mainportion of the first receptacle and the second cylindrical member isdisposed in the main portion of the second receptacle.

Each of the first receptacle and the second receptacle further includesan opening which extends outward from the main portion and is positionedgenerally about a central reference line.

The opening of each of the first receptacle and the second receptacleincludes a first portion defined by generally parallel surfaces whichextend outward from the main portion and define a minimum opening widthof each of the first receptacle and the second receptacle, and whenmoving from the first state to the second state at least one of thefirst cylindrical member passes through the first portion of the firstreceptacle or the second cylindrical member passes through the firstportion of the second receptacle.

The opening of each of the first receptacle and the second receptaclemay further include a flared portion extending outward from the firstportion in which the opening widens from the minimum opening width.

Each of the first cylindrical member and the second cylindrical membermay be defined by an outer diameter which is greater than the minimumwidth and less than twice the radial distance.

Such needs are also met by embodiments of the disclosed concept whichare directed to a trip unit. The trip unit comprises: a housing and anaccess door. The housing includes a first receptacle and a secondreceptacle formed thereon or therein. The access door includes a firstcylindrical member extending along a hinge axis in a first direction, asecond cylindrical member extending along the hinge axis in a seconddirection opposite the first direction, and a thickened portion having acontoured outer surface disposed adjacent the first cylindrical memberand the second cylindrical member. The access door is moveable from: (i)a first state wherein the first cylindrical member is disposed in thefirst receptacle and the second cylindrical member is disposed in thesecond receptacle such that the access door is coupled to the housingand generally free to rotate about the hinge axis through at least apredetermined degree range, and (ii) a second state in which the accessdoor is decoupled from the housing responsive to the access door beingrotated beyond the predetermined degree range and the contoured outersurface interacting with a portion of the housing.

Each of the first receptacle and the second receptacle may comprise amain portion defined at least in-part by a curved surface disposedgenerally a radial distance about the hinge axis, and when disposed inthe first state, the first cylindrical member is disposed in the mainportion of the first receptacle and the second cylindrical member isdisposed in the main portion of the second receptacle.

Each of the first receptacle and the second receptacle may furtherinclude an opening which extends outward from the main portion and ispositioned generally about a central reference line oriented at an angleabout the hinge axis to a reference plane disposed parallel to the afront face of the housing and in which the hinge axis lies.

The opening of each of the first receptacle and the second receptaclemay include a first portion defined by generally parallel surfaces whichextend outward from the main portion and define a minimum opening widthof each of the first receptacle and the second receptacle, and whenmoving from the first state to the second state at least one of thefirst cylindrical member passes through the first portion of the firstreceptacle or the second cylindrical member passes through the firstportion of the second receptacle.

The opening of each of the first receptacle and the second receptaclemay further include a flared portion extending outward from the firstportion in which the opening widens from the minimum opening width.

Each of the first cylindrical member and the second cylindrical membermay be defined by an outer diameter which is greater than the minimumwidth and less than twice the radial distance.

Such needs are also met by embodiments of the disclosed concept whichare directed to a circuit breaker. The circuit breaker comprises ahousing and a trip unit selectively coupled to the housing. The housingincludes a front cover selectively coupled to the housing, the frontcover including an opening defined therethrough. The trip unit comprisesa trip unit housing including a first receptacle and a second receptacleformed thereon or therein and a front face accessible via the opening ofthe front cover when the front cover is coupled to the housing. Thefront face includes a number of adjustment mechanisms for adjusting oneor more characteristics of the trip unit. The trip unit furthercomprises an access door having a first cylindrical member extendingalong a hinge axis in a first direction, a second cylindrical memberextending along the hinge axis in a second direction opposite the firstdirection, and a thickened portion having a contoured outer surfacedisposed adjacent the first cylindrical member and the secondcylindrical member. When the front cover is uncoupled from the housing,the access door is moveable from: (i) a first state wherein the firstcylindrical member is disposed in the first receptacle and the secondcylindrical member is disposed in the second receptacle such that theaccess door is coupled to the housing and generally free to rotate aboutthe hinge axis through at least a first predetermined degree range, and(ii) a second state in which the access door is decoupled from thehousing responsive to the access door being rotated beyond the firstpredetermined degree range and the contoured outer surface interactingwith a portion of the housing. When the access door is disposed in thefirst state and the front cover is coupled to the housing, the frontcover restricts rotation of the access door about the hinge axis to asecond predetermined degree range less than the first predetermineddegree range.

Each of the first receptacle and the second receptacle may comprise amain portion defined at least in-part by a curved surface disposedgenerally a radial distance about the hinge axis, and when disposed inthe first state, the first cylindrical member is disposed in the mainportion of the first receptacle and the second cylindrical member isdisposed in the main portion of the second receptacle.

Each of the first receptacle and the second receptacle may furtherinclude an opening which extends outward from the main portion and ispositioned generally about a central reference line oriented at an angleabout the hinge axis to a reference plane disposed parallel to the afront face of the housing and in which the hinge axis lies.

The opening of each of the first receptacle and the second receptaclemay include a first portion defined by generally parallel surfaces whichextend outward from the main portion and define a minimum opening widthof each of the first receptacle and the second receptacle, and whenmoving from the first state to the second state at least one of thefirst cylindrical member passes through the first portion of the firstreceptacle or the second cylindrical member passes through the firstportion of the second receptacle.

The opening of each of the first receptacle and the second receptaclemay further include a flared portion extending outward from the firstportion in which the opening widens from the minimum opening width.

Each of the first cylindrical member and the second cylindrical membermay be defined by an outer diameter which is greater than the minimumwidth and less than twice the radial distance.

BRIEF DESCRIPTION OF THE DRAWINGS

A full understanding of the disclosed concept can be gained from thefollowing description of the preferred embodiments when read inconjunction with the accompanying drawings in which:

FIG. 1 is an isometric view of a circuit breaker including a trip unithaving an access door in accordance with an example embodiment of thedisclosed concept shown in a closed position;

FIG. 2 is an isometric view of the circuit breaker of FIG. 1 showing theaccess door disposed in an open position;

FIG. 3 is an isometric view of the trip unit of the circuit breaker ofFIG. 1 shown with the access door disposed in a closed position;

FIG. 4 is an isometric view of the trip unit of the circuit breaker ofFIG. 1 shown with the access door disposed in an open position;

FIG. 5 is a sectional view of a portion of the trip unit and access doorof FIG. 3 taken along line 5-5 thereof;

FIG. 6 is a sectional view of a portion of the trip unit and access doorof FIG. 4 taken along line 6-6 thereof;

FIG. 7 is a sectional view of a portion of the trip unit and access doorof FIG. 1 taken along line 7-7 thereof;

FIG. 8 is an exploded isometric view of the trip unit of FIG. 3 shownwith an access door thereof uncoupled from the housing of the trip unit;and

FIG. 9 is a detail view of a portion of the sectional view of FIG. 5.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Directional phrases used herein, such as, for example, left, right,front, back, top, bottom and derivatives thereof, relate to theorientation of the elements shown in the drawings and are not limitingupon the claims unless expressly recited therein.

As employed herein, the word “number” shall mean a quantity of one, orany integer greater than one (i.e., a plurality).

As employed herein, the statement that two or more parts are “coupled”together shall mean that the parts are joined together either directlyor joined through one or more intermediate parts.

As employed herein, the statement that two or more parts are“selectively coupled” shall mean that the parts are secured togethereither directly or through one or more intermediate parts in a mannerwhich may be readily undone.

A circuit breaker 10 in accordance with an example embodiment of thedisclosed concept is shown in FIGS. 1 and 2. The circuit breaker 10includes a molded housing 12 having a front cover 14 selectively coupledthereto via a number of suitable fasteners 16 (e.g., without limitation,screws). In an example embodiment in accordance with the disclosedconcept, housing 12 was formed from Rosite 6060D Pantone 432 and frontcover 14 was formed from Valox 3706 ANSI 61. It is to be appreciated,however, that other suitable materials may be employed without varyingfrom the scope of the disclosed concept. Circuit breaker 10 includes aremovable trip unit 18 (shown in greater detail in FIGS. 3 and 4)coupled to the housing 12 having a front face 20 accessible via anopening 22 defined in front cover 14.

Referring to FIGS. 3 and 4, the front face 20 of the trip unit 18 formspart of a trip unit housing 24, which houses circuitry and relatedelements (not shown) disposed therein for controlling operation of thecircuit breaker 10. In an example embodiment in accordance with thedisclosed concept, the trip unit housing 24 was formed from Sabic Valox732E with the front face 20 having an adhesive overlay placed on thehousing 24. It is to be appreciated, however, that other suitablematerials may be employed without varying from the scope of thedisclosed concept. Front face 20 includes a number of adjustmentmechanisms 26 (FIG. 4) for adjusting one or more characteristics of thetrip unit 18. In order to allow for selective access to the adjustmentmechanisms 26, the trip unit 18 further includes an access door 30 whichis rotatably coupled to the trip unit housing 24 via a hinge assembly 40such that the access door 30 is rotatable about a hinge axis 42 fromamong a closed position (such as shown in FIGS. 1 and 3) in which theaccess door 30 restricts access to the adjustment mechanisms 26, and anopen position (such as shown in FIGS. 2 and 4) in which the access doordoes not restrict access to the adjustment mechanisms 26. In an exampleembodiment in accordance with the disclosed concept, the access door 30was formed from Sabic LEXAN 141R clear. It is to be appreciated,however, that other suitable materials may be employed without varyingfrom the scope of the disclosed concept.

Continuing to refer to FIGS. 3 and 4 as well as to the additional viewsof FIGS. 5-9, hinge assembly 40 is formed in-part by portions of theaccess door 30 and in-part by portions of the trip unit housing 24. Moreparticularly, hinge assembly 40 includes a first receptacle 44 and asecond receptacle 45 formed in or on the trip unit housing 24. Referringto the detail view of FIG. 9, the first receptacle 44 includes a mainportion 46 defined at least in-part by a curved surface 47 disposedgenerally a radial distance r about the hinge axis 42. First receptacle44 further includes an opening 48 which extends outward from the mainportion 46 and is positioned generally about a central reference line Cextending from the hinge axis 42 and oriented at an angle θ (FIG. 5)about the hinge axis 42 to a reference plane P disposed parallel to thefront face 20 of the trip unit 18 and in which the hinge axis 42 lies.In examples of the disclosed concept, angles θ less than 90° were foundto be unsuitable. Opening 48 includes a first portion 50 defined bygenerally parallel surfaces which extend outward from the main portion46 and define a minimum opening width w of the first receptacle 44.Extending outward from the first portion 50 is a flared portion 52 inwhich opening 48 widens from the minimum opening width w. Secondreceptacle 45 is of generally similar shape and form as the firstreceptacle 44 and thus is not further described herein. The generalpurpose of such arrangement of each of the first and second receptacles44, 45 will be discussed in detail further below. In an exampleembodiment in accordance with the disclosed concept, each of the firstreceptacle 44 and the second receptacle 45 were formed with a minimumopening width w of 0.060 in, an curved surface disposed a radialdistance r of 0.047 in from the hinge axis 42, and a main portiondisposed about a central reference line C disposed at 135° with respectto the reference plane P. It is to be appreciated, however, that othersuitable values for such dimensions may be employed without varying fromthe scope of the disclosed concept.

In addition to the first and second receptacle portions 44, 45, thehinge assembly 40 further includes corresponding portions of the accessdoor 30 which interact with the portions of the trip unit housing 24.More particularly, referring to FIGS. 3 and 8, hinge assembly 40includes a first cylindrical member 60 extending from the access door 30along the hinge axis 42 in a first direction and a second cylindricalmember 62 extending from the access door 30 along the hinge axis 42 in asecond direction opposite the first direction. Each of the first andsecond cylindrical members 60 and 62 are of generally similar shape andconstruction and as shown in the sectional view of FIG. 5 are generallydefined by an outer diameter d. As shown in the sectional views of FIGS.5-7 and 9, the first cylindrical member 60 is sized to be disposed inthe main portion 46 of first receptacle 44 (and similarly the secondcylindrical member 62 in the corresponding portion of the secondreceptacle 45) such that the door 30 is coupled to, and generally freeto rotate about hinge axis 42 from among a closed position (such asshown in FIGS. 1 and 3) and an open position (such as shown in FIGS. 2and 4). Although not discussed in detail herein, it is to be appreciatedthat one or more suitable latching or locking mechanisms (not numbered)may be provided for securing the access door 30 in a closed position(such as shown in FIGS. 1 and 3) without varying from the scope of thedisclosed concept.

In addition to the first and second cylindrical members 60 and 62, theaccess door 30 further includes a thickened portion 72 having acontoured outer surface 70 disposed adjacent the first and secondcylindrical members 60 and 62 which are portions of the hinge assembly40. The function of such features are discussed in detail below.

Having thus described the basic components and arrangement of the hingeassembly 40, benefits of such arrangement in regard to the assembly andpotential disassembly thereof will now be discussed. In order toassemble the hinge assembly 40 (i.e., couple the access door 30 to thetrip unit housing 24), each of the first and second cylindrical members60 and 62 are first aligned with the corresponding openings (e.g., 48)of the first and second receptacles 44 and 45. The flared portion (e.g.,52) of each receptacle assists in centering the respective cylindricalmember within the corresponding opening. Once both cylindrical membersare centered in the openings of the respective receptacles, each of thecylindrical members are displaced through the first portion (e.g., ofeach opening via application of a suitable force applied to the accessdoor 30 at or near each of the cylindrical members 60, 62 such that eachof the cylindrical members “snaps” into the corresponding main portion(e.g., 46) of the respective receptacle. Accordingly, it is to beappreciated that access door 30 is generally “snap fit” to the trip unithousing 24.

In addition to providing a ready snap fit assembly of the access door 30to the trip unit housing 24, the hinge assembly 40 further allows forthe access door 30 to readily detach from the trip unit housing 24without damaging either the housing 24 or the door 30 in instances whereknown arrangements would typically break, and thus necessitate the needfor replacement of one or both of the access door or the trip unithousing (which would necessitate replacement of the entire trip unit).As previously discussed, such an instance where failure commonly occursis when the access door of a trip unit is opened beyond its intendedrange, such as readily occurs if the access door 30 is contacted whiledisposed in an open position such as by a technician moving in thevicinity of the access door or by attempting to install the front coverof a circuit breaker without having first closed the access door of thetrip unit. FIGS. 4 and 6 show the trip unit 18, as previously described,with the access door 30 disposed in a fully open position. Such fullyopen position reached when the outer surface 70 of the thickened portion72 of the access door 30 bears against a portion of the trip unithousing 24 and occurs when the access door 30 has been rotated throughpredetermined degree range α (FIG. 6) from the closed position (FIG. 5)about the hinge axis 30.

Referring to the sectional view of FIG. 6, if a force (shown generallyby the arrow F) is applied to the access door 30 when the access door 30is disposed in such full open position, the point of interaction (notnumbered) between the outer surface 70 of the thickened portion 72 withthe trip unit housing 24 relative to the location of the firstcylindrical member 60 positioned within the main portion 46 of the firstreceptacle 44 results in the first cylindrical member 60 being forcedgenerally along a path such as shown by the arrow P. As the path Ppasses generally along the central reference line C of the opening 48,the first cylindrical member 60 is thus forced from the first receptacle44 (and similarly the second cylindrical member 62 is forced from thesecond receptacle 45) in a manner generally reverse to the snap fitassembly process previously described (i.e., one or both of thecylindrical members 60 and 62 are displaced outward through the firstopening of the corresponding receptacle 44, 45). Through such movement,the access door 30 is readily un-snap fitted from the trip unit housing24 in a manner that results in the access door 30 being uncoupled fromthe trip unit housing 24 without causing damage to any portion of thehinge assembly 40. In the example illustrated arrangement, such snapuncoupling begins to occur when the access door 30 is opened beyond apredetermined degree range α of approximately 190° and completelyuncouples at about 195°. It is to be appreciated, however, that thepoint of such snap uncoupling may be adjusted to fit a particularapplication by varying the angular placement of the centerline C onwhich the opening of the receptacles are centered along with varying theprofile of the outer surface 70 of the thickened portion 72 of theaccess door 30.

In contrast to the functioning described in conjunction with FIGS. 4 and6, FIG. 7 shows an example of the illustrated embodiment in operationwhen the front cover 14 is secured to the housing 12 of the circuitbreaker 10 such that the front face 20 of the trip unit 18 is disposedin opening 22 of the front cover. If a force (shown generally once againby the arrow F) is applied to the access door 30 when the access door 30is disposed in a full open position, which is restricted to a lesseropening predetermined degree range α′ (as compared to the angle α, FIG.6) due to the presence of the front cover 14 adjacent the trip unithousing 24, the interaction of the outer surface 70 of the thickenedportion 72 with the front cover 14 of the circuit breaker 10 (incontrast to the interaction with the trip unit housing 24) results inthe first cylindrical member 60 being forced generally along a pathshown by the arrow P′. As the path P′ does not pass along the centralreference line C of the opening 48, but instead tends to be directedtoward the curved surface 47 of the main portion 46 of the firstreceptacle 44, the first cylindrical member 60 is retained in the firstreceptacle 44 (and similarly the second cylindrical member 62 isretained in the second receptacle 45) and thus the access door 30 doesnot undesirably unsnap from the trip unit housing 24.

From the foregoing description, it is to be appreciated that thedisclosed concept provides for an access door that is less likely to bedamaged by a technician than existing arrangements. Further, the conceptprovides for an access door that will not be undesirably detached by auser of the circuit breaker who is merely accessing the adjustmentmechanisms of the trip unit.

While example embodiments of the disclosed concept have been shown withrespect to an access door of a trip unit, it is also contemplated thatthe disclosed concept may be employed in other applications whereselective uncoupling of an access door or similar structure would bedesirable.

While specific embodiments of the disclosed concept have been describedin detail, it will be appreciated by those skilled in the art thatvarious modifications and alternatives to those details could bedeveloped in light of the overall teachings of the disclosure.Accordingly, the particular arrangements disclosed are meant to beillustrative only and not limiting as to the scope of the disclosedconcept which is to be given the full breadth of the claims appended andany and all equivalents thereof

What is claimed is:
 1. A hinge assembly comprising: a first portionhaving a first receptacle and a second receptacle; and a second portionhaving a first cylindrical member extending along a hinge axis in afirst direction, a second cylindrical member extending along the hingeaxis in a second direction opposite the first direction, and a thickenedportion having a contoured outer surface disposed adjacent the firstcylindrical member and the second cylindrical member, wherein the secondportion is moveable from: (i) a first state wherein the firstcylindrical member is disposed in the first receptacle and the secondcylindrical member is disposed in the second receptacle such that thesecond portion is coupled to the first portion and generally free torotate about the hinge axis through at least a predetermined degreerange, and (ii) a second state in which the second portion is decoupledfrom the first portion responsive to the second portion being rotatedbeyond the predetermined degree range and the contoured outer surfaceinteracting with a portion of the first portion.
 2. The hinge assemblyof claim 1, wherein each of the first receptacle and the secondreceptacle comprises a main portion defined at least in-part by a curvedsurface disposed generally a radial distance about the hinge axis, andwherein when disposed in the first state, the first cylindrical memberis disposed in the main portion of the first receptacle and the secondcylindrical member is disposed in the main portion of the secondreceptacle.
 3. The hinge assembly of claim 2, wherein each of the firstreceptacle and the second receptacle further includes an opening whichextends outward from the main portion and is positioned generally abouta central reference line.
 4. The hinge assembly of claim 3, wherein theopening of each of the first receptacle and the second receptacleincludes a first portion defined by generally parallel surfaces whichextend outward from the main portion and define a minimum opening widthof each of the first receptacle and the second receptacle, and whereinwhen moving from the first state to the second state at least one of thefirst cylindrical member passes through the first portion of the firstreceptacle or the second cylindrical member passes through the firstportion of the second receptacle.
 5. The hinge assembly of claim 4,wherein the opening of each of the first receptacle and the secondreceptacle further includes a flared portion extending outward from thefirst portion in which the opening widens from the minimum openingwidth.
 6. The hinge assembly of claim 4, wherein each of the firstcylindrical member and the second cylindrical member are defined by anouter diameter which is greater than the minimum width and less thantwice the radial distance.
 7. A trip unit comprising: a housingincluding a first receptacle and a second receptacle formed thereon ortherein; and an access door having a first cylindrical member extendingalong a hinge axis in a first direction, a second cylindrical memberextending along the hinge axis in a second direction opposite the firstdirection, and a thickened portion having a contoured outer surfacedisposed adjacent the first cylindrical member and the secondcylindrical member, wherein the access door is moveable from: (i) afirst state wherein the first cylindrical member is disposed in thefirst receptacle and the second cylindrical member is disposed in thesecond receptacle such that the access door is coupled to the housingand generally free to rotate about the hinge axis through at least apredetermined degree range, and (ii) a second state in which the accessdoor is decoupled from the housing responsive to the access door beingrotated beyond the predetermined degree range and the contoured outersurface interacting with a portion of the housing.
 8. The trip unit ofclaim 7, wherein each of the first receptacle and the second receptaclecomprises a main portion defined at least in-part by a curved surfacedisposed generally a radial distance about the hinge axis, and whereinwhen disposed in the first state, the first cylindrical member isdisposed in the main portion of the first receptacle and the secondcylindrical member is disposed in the main portion of the secondreceptacle.
 9. The trip unit of claim 8, wherein each of the firstreceptacle and the second receptacle further includes an opening whichextends outward from the main portion and is positioned generally abouta central reference line oriented at an angle about the hinge axis to areference plane disposed parallel to the a front face of the housing andin which the hinge axis lies.
 10. The trip unit of claim 9, wherein theopening of each of the first receptacle and the second receptacleincludes a first portion defined by generally parallel surfaces whichextend outward from the main portion and define a minimum opening widthof each of the first receptacle and the second receptacle, and whereinwhen moving from the first state to the second state at least one of thefirst cylindrical member passes through the first portion of the firstreceptacle or the second cylindrical member passes through the firstportion of the second receptacle.
 11. The trip unit of claim 10, whereinthe opening of each of the first receptacle and the second receptaclefurther includes a flared portion extending outward from the firstportion in which the opening widens from the minimum opening width. 12.The trip unit of claim 10, wherein each of the first cylindrical memberand the second cylindrical member are defined by an outer diameter whichis greater than the minimum width and less than twice the radialdistance.
 13. A circuit breaker comprising: a housing including a frontcover selectively coupled to the housing, the front cover including anopening defined therethrough; and a trip unit selectively coupled to thehousing, the trip unit comprising: a trip unit housing including a firstreceptacle and a second receptacle formed thereon or therein and a frontface accessible via the opening of the front cover when the front coveris coupled to the housing, the front face having a number of adjustmentmechanisms for adjusting one or more characteristics of the trip unit;and an access door having a first cylindrical member extending along ahinge axis in a first direction, a second cylindrical member extendingalong the hinge axis in a second direction opposite the first direction,and a thickened portion having a contoured outer surface disposedadjacent the first cylindrical member and the second cylindrical member,wherein, when the front cover is uncoupled from the housing, the accessdoor is moveable from: (i) a first state wherein the first cylindricalmember is disposed in the first receptacle and the second cylindricalmember is disposed in the second receptacle such that the access door iscoupled to the housing and generally free to rotate about the hinge axisthrough at least a first predetermined degree range, and (ii) a secondstate in which the access door is decoupled from the housing responsiveto the access door being rotated beyond the first predetermined degreerange and the contoured outer surface interacting with a portion of thehousing, and wherein, when the access door is disposed in the firststate and the front cover is coupled to the housing, the front coverrestricts rotation of the access door about the hinge axis to a secondpredetermined degree range less than the first predetermined degreerange.
 14. The circuit breaker of claim 13, wherein each of the firstreceptacle and the second receptacle comprises a main portion defined atleast in-part by a curved surface disposed generally a radial distanceabout the hinge axis, and wherein when disposed in the first state, thefirst cylindrical member is disposed in the main portion of the firstreceptacle and the second cylindrical member is disposed in the mainportion of the second receptacle.
 15. The circuit breaker of claim 14,wherein each of the first receptacle and the second receptacle furtherincludes an opening which extends outward from the main portion and ispositioned generally about a central reference line oriented at an angleabout the hinge axis to a reference plane disposed parallel to the afront face of the housing and in which the hinge axis lines.
 16. Thecircuit breaker of claim 15, wherein the opening of each of the firstreceptacle and the second receptacle includes a first portion defined bygenerally parallel surfaces which extend outward from the main portionand define a minimum opening width of each of the first receptacle andthe second receptacle, and wherein when moving from the first state tothe second state at least one of the first cylindrical member passesthrough the first portion of the first receptacle or the secondcylindrical member passes through the first portion of the secondreceptacle.
 17. The circuit breaker of claim 16, wherein the opening ofeach of the first receptacle and the second receptacle further includesa flared portion extending outward from the first portion in which theopening widens from the minimum opening width.
 18. The circuit breakerof claim 16, wherein each of the first cylindrical member and the secondcylindrical member are defined by an outer diameter which is greaterthan the minimum width and less than twice the radial distance.